Method of finishing a stone surface and abrasive article

ABSTRACT

A structured abrasive article comprises a structured abrasive layer adhered to a major surface of a backing, the structured abrasive layer comprising shaped abrasive composites adhered to the major surface, the shaped abrasive composites comprising milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a median particle size D 50  of from 3 to 30 microns. In a method of finishing a stone surface, the structured abrasive layer is frictionally contacting with the stone surface; and moved relative to the stone surface under conditions sufficient to finish the stone surface.

TECHNICAL FIELD

The present disclosure broadly relates to methods of finishing a stone surface and structured abrasive articles.

BACKGROUND

Flooring and counters made of hard composite materials are widely used. Such hard composite materials are collectively referred to by those engaged in the field of hard surface finishing as “stone” or “stone surfaces”. These people are involved in the practice of producing surfaces with maximized aesthetic appearance (e.g., high gloss and reflected image clarity); typically, including a dry finishing process.

For ease of reference, the term “stone”, as used hereinafter, refers to durable naturally-occurring mineral materials as well as rigid durable man-made composite materials containing a predominant mineral phase. Examples include naturally-occurring minerals (e.g., granite, limestone, travertine, onyx, or marble) or man-made composites (e.g., cementitious terrazzo, and resin-bonded terrazzo), ceramic tile, and concrete).

To achieve a highly polished stone surface, the art has relied on ultra-hard diamond particles in lofty nonwoven abrasive constructions. Diamond abrasives are conventionally used in a series of progressively finer particle sizes to refine stone surfaces to high aesthetic levels (e.g. high-brightness, high-clarity reflected image quality). Surface parameters such as, for example, “gloss”, “specular reflectivity”, “haze”, and/or “distinctness of image” (DOI) are typically used to characterize the aesthetic appearance of polished stone surfaces. These measured surface parameters correlate well with perceived favorability of the surface as discriminated by eye. For a floor surface, haze (which is a measure of the cloudiness of a reflected image) and DOI (which is a measure of the clarity or sharpness of an image reflected off the surface) are generally the most important visual aesthetic parameters. A high gloss value, signifying the brightness or shininess of a surface, may not be aesthetically sufficient if not accompanied by a high DOI value or sharp image clarity. Highly aesthetically desirable surfaces generally exhibit very high DOI, low haze, and at least a medium gloss level.

Diamond abrasives, as their name suggests, are typically expensive. It would be desirable to have lower cost and/or improved methods of finishing stone surfaces.

SUMMARY

The present disclosure provides a lower cost alternative to diamond abrasives for finishing stone floors to high aesthetic levels, which can surpass those achieved through conventional diamond abrasive methods. Unexpectedly, the present disclosure achieves these high, or even superior, aesthetic levels of appearance using less hard and coarser abrasive materials than are used in diamond abrasive finishing.

In one aspect, the present disclosure provides a method of finishing a stone surface, the method comprising:

providing a structured abrasive article comprising a structured abrasive layer adhered to a major surface of a backing, the structured abrasive layer comprising shaped abrasive composites adhered to the major surface, the shaped abrasive composites comprising milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a median particle size D₅₀ of from 3 to 30 microns;

frictionally contacting the structured abrasive layer with the stone surface; and

moving the structured abrasive layer relative to the stone surface under conditions sufficient to finish the stone surface.

In another aspect, the present disclosure provides a structured abrasive article suitable for practicing methods of finishing a stone surface according to the present disclosure. The structured abrasive article comprises a structured abrasive layer adhered to a major surface of a backing, wherein the structured abrasive layer comprises shaped abrasive composites adhered to the major surface, wherein the shaped abrasive composites comprise milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a mean particle size D₅₀ of from 3 to 30 microns.

As used herein,

“D₅₀” refers to the median particle size (i.e. equivalent spherical diameter) of a particle size distribution measured consistent with ISO 13320:2009, “Particle size analysis—Laser diffraction methods”.

“Fracture toughness” is determined consistent with the method described by P. J. Blau and B. R. Lawn, “Indentation of Brittle Materials” in Microindentation Techniques In Materials Science And Engineering, ASTM Special Technical Publication 889, P. J. Blau and B. R. Lawn, Eds., 1985, pp. 26-46, ASTM Philadelphia, Pa.;

the term “milled” means mechanically comminuted in a mill such as, for example, a ball mill, planetary ball mill, pebble mill, rod mill, vertical shaft impactor mill, roller mill, or jet mill;

the term “polymeric” refers to an organic polymer; and

“Vickers hardness” is determined consistent with ASTM Test Method E384-11 (editorially corrected March 2012), “Standard Test Method for Knoop and Vickers Hardness of Materials”.

Distinctness of Image (DOI), gloss, and haze, is determined consistent with ASTM E430-11 (2011). “Standard Test Methods for Measurement of Gloss of High-Gloss Surfaces by Abridged Goniophotometry”.

Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top-view of exemplary structured abrasive disc 10.

FIG. 2 is a schematic cross-sectional side view of structured abrasive disc 10 taken along plane 2-2.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. The figures may not be drawn to scale. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure.

DETAILED DESCRIPTION

Without wishing to be bound by theory, the present inventor believes that in processes according to the present disclosure, the stone surface undergoes a brittle to ductile state transition due to action of the structured abrasive article. This results from the physical properties (e.g., hardness, toughness, and few cutting points) of the milled polycrystalline ceramic abrasive particles in combination with the structured abrasive article construction. Once in the ductile state, the material smears and then reverts to the brittle state thereby resulting in a smooth high clarity surface finish. This contrasts with diamond abrasives, which are typically single crystal and have numerous points per crystal.

Materials with surfaces that can be finished according to the methods of the present disclosure include durable naturally-occurring mineral materials as well as rigid durable man-made composite materials containing a predominant mineral phase. Examples include granite, limestone, travertine, onyx, marble, cementitious terrazzo, resin-bonded terrazzo, ceramic tile, concrete, and combinations thereof.

The materials may be in any form such as, for example, in the form of a floor, counter, wall, pillar, monument, plaza, table top, sculpture, or patio. In such cases, the surfaces finished are generally exposed to viewing by a user.

Characterization of stone surfaces before, during, and/or after finishing may be characterized by any suitable technique. Examples of useful parameters include gloss, specular reflectivity, distinctness of image (DOI), and haze. Suitable measurement techniques for these parameters are known in the art (e.g., as available from standards organizations such as ASTM International, West Conshohocken, Pa.).

In typical use, structured abrasive articles according to the present disclosure are affixed to a backup/driver pad mounted on a tool, although this not a requirement. Examples of suitable tools include: (a) for stone floors; floor machines having a driven lofty nonwoven driver pad, low-speed 180 rpm swing machine, a battery electric ride-on or walk-behind floor machine, or a high-speed >1400 rpm (e.g., propane) floor machine operated at travel speed in excess of normal use; and (b) for non-floor stone surfaces; handheld random orbital tool, handheld rotary tool, and handheld, planetary tools. With floor machines, the driver pad is typically a lofty open nonwoven disc such as, for example, that available as 3M 4100 WHITE SUPER POLISH PAD or 5100 RED BUFFER PAD from 3M Company.

In some embodiments, it may be useful to employ one or more grinding and/or honing steps prior to finishing the stone surface according to the present disclosure. Such techniques are well known to those of ordinary skill in the art.

Unexpectedly, when using methods and structured abrasive articles according to the present disclosure, floor machines having a rotational speed of 180 to 300 revolutions per minute (rpm), preferably less than 200 rpm, typically outperform high speed finishing machines in terms of aesthetic appearance if used for comparable times under normal use conditions.

An exemplary structured abrasive disc 10, useful for practicing the method of the present disclosure, is shown in FIGS. 1 and 2.

FIG. 1 shows exemplary structured abrasive disc 10, which has an array of hexagonal-post-shaped abrasive composites 18 separated from adjacent shaped abrasive composites by a network valley region 28. The structured abrasive article can be, for example, in the form of an abrasive disc (as shown) or other common converted form such as an endless belt.

As shown in FIG. 2, structured abrasive layer 14 includes a plurality of shaped abrasive composites 18 that are bonded to backing 12. Backing 12 has first side 12 a and second side 12 b. Shaped abrasive composites 18 comprise abrasive particles 15 dispersed and retained in polymeric binder matrix 16. Second side 12 b of backing 12 is attached to optional foam layer 20 on first side 20 a of foam layer 20 by optional first adhesive layer 22. Optional attachment layer 26 (shown as one part of a two-part mechanically interlocking fastener system), to attach the structure abrasive disc 10 to a platen of a grinding or finishing machine, is affixed to second side 20 b of foam layer 20 by second adhesive layer 24. Instead of one part of a two-part interlocking fastener system (e.g. hook and loop) to attach the abrasive article to a grinding tool, other attachment systems such as adhesives, or other types of interlocking and/or mechanical fasteners can also be used.

Exemplary suitable shaped abrasive composite shapes include, without limitation: rods, cones, truncated cones; rhomboid, triangular, rectangular, hexagonal, or square posts; and rhomboid, triangular, rectangular, hexagonal, or square truncated pyramids. In one embodiment, the top of each shaped abrasive composite is planar such that the shaped abrasive composite does not come to a peak or a tip; however, pyramidal or conical shaped abrasive composites can be used in some applications.

The spacing of the shaped abrasive composites may vary from about 0.3 shaped abrasive composites per linear cm to about 100 shaped abrasive composites per linear cm, or about 0.4 to about 20 shaped abrasive composites per linear cm, or about 0.5 to 10 shaped abrasive composites per linear cm, or about 0.6 to 3.0 shaped abrasive composites per linear cm. In one aspect of the abrasive article, there are at least about 1 shaped abrasive composite per square centimeter (cm²) or at least about 5 shaped abrasive composites per square centimeter (cm²). In a further embodiment of the disclosure, the area spacing of shaped abrasive composites ranges from about 1 to about 200 shaped abrasive composites/cm², or from about 2 to about 10 shaped abrasive composites/cm².

The height of the abrasive composites as measured from the top of the valley between adjacent shaped abrasive composites to the top of the shaped abrasive composite is constant across structured abrasive article, but it is possible to have shaped abrasive composites of varying heights. The height of the shaped abrasive composites may be a value from about 10 microns to about 25,000 microns (2.5 cm), or about 25 to about 15,000 microns, or from about 100 to about 10,000 microns, or from about 500 to about 4,000 microns.

In various embodiments, the bearing area ratio can be between about 20 percent to about 80 percent, or between about 40 percent to about 70 percent, or between about 50 percent to about 70 percent. The bearing area ratio, expressed as a percentage, is the ratio of the total area of the shaped abrasive composites 18 to the total area of the abrasive article including the area of the network valley region 28. Depending on the application or the workpiece, a larger or smaller bearing area ratio may desirable depending on the grade of abrasive, the work piece material, the unit loading pressure, and the desired cut rate and finish.

Suitable backings include those known useful in abrasive articles, such as polymeric film, cloth including treated cloth, paper, foam, nonwoven, treated or primed versions thereof, and combinations thereof. Examples include polyester films, polyolefin films (e.g., polyethylene and propylene film), polyamide films, and polyimide films. A thin backing can be reinforced using another layer for support, such as a thicker film, or a polycarbonate sheet, for example. In addition, the abrasive article can be attached to a base or sheet or directly to a finishing apparatus or machine via any known route, for example, adhesives including pressure sensitive adhesives are useful.

The backing serves the function of providing a support for the shaped abrasive composites. The backing should be capable of adhering to the polymeric binder matrix after exposure of binder precursor to curing conditions, and be strong and durable so that the resulting abrasive article is long lasting. In some embodiments, the backing may be sufficiently flexible so that the articles used in the inventive method may conform to surface contours, radii, and irregularities in the workpiece. In other embodiments, the backing may be rigid.

As mentioned, the backing may be a polymeric film, paper, vulcanized fiber, a molded or cast elastomer, a treated nonwoven backing, or a treated cloth. Examples of polymeric films include polyester films, co-polyester films, polyimide films, and polyamide films. Porous backings (e.g., woven, knit, or nonwoven (including paper) backings) may be saturated with a thermosetting and/or thermoplastic material to provide the desired properties. Any of the above backing materials may further include additives such as, for example, fillers, fibers, dyes, pigments, wetting agents, coupling agents, and plasticizers. In one embodiment, the backing is about 0.05 millimeter (mm) to about 5 mm thick.

If present, the optional foam layer may be open cell and/or closed cell, and may be stiff or soft. Preferably, the optional foam layer has a thickness of less than 1 centimeter (cm), more preferably less than 0.5 cm. In some embodiments, the foam layer is substantially uniform in thickness.

The milled polycrystalline ceramic abrasive particles will now be discussed in greater detail.

First of all, the milled polycrystalline ceramic abrasive particles are milled. During the milling process, cutting points are successively reduced by mechanical comminution in a mill, resulting in blocky abrasive particles with few or no cutting points (e.g., in contrast to diamond crystals which have many cutting points).

Second, the milled polycrystalline ceramic abrasive particles are polycrystalline ceramics. That is, the ceramic material in each abrasive particle comprises a plurality of discrete crystallites characterized by discrete boundaries. In some embodiments, a separate, compositionally distinct, crystalline phase may be present throughout the milled polycrystalline ceramic abrasive particles, which serves to inhibit crack propagation. Preferably, the crystallites have an average size of less than 0.5 micron, more preferably less than 0.3 micron, and more preferably less than 0.1 micron.

Alumina-based polycrystalline ceramic abrasive particles may comprise only alumina, or alternatively alumina in combination with one or more metal oxides other than alumina such as rare earth oxide, yttria, iron oxide, titania, including materials of or containing complex Al₂O₃-metal oxides (e.g. Dy₃Al₅O₁₂, Y₃Al₅O₁₂, or CeAl₁₁O₁₈). The Al₂O₃ source may also include, for example, minor amounts of silica, iron oxide, titania, and carbon.

Preferably, the shaped abrasive composites are essentially free of ceramic abrasive particles other than the milled polycrystalline ceramic abrasive particles, although secondary ceramic abrasive particles that are less hard than the milled polycrystalline ceramic abrasive particles may be acceptable in some applications where the workpiece is harder than the secondary ceramic abrasive particles. Preferably, the shaped abrasive composites contain less than 5 percent by weight, preferably less than 1 percent by weight, and more preferably less than 0.1 percent by weight of ceramic particles other than the milled polycrystalline ceramic abrasive particles.

Any milled polycrystalline ceramic material may be used including, for example, alumina-based ceramics, and zirconia-based ceramics. Preferably, the milled polycrystalline ceramic material comprises at least 70 percent by weight, 80 percent by weight, 90 percent by weight, 95 percent by weight, 99 percent by weight, or even 100 percent by weight of polycrystalline ceramic alumina.

The milled polycrystalline ceramic abrasive particles have a median particle size D₅₀ of from 3 to 30 microns; preferably from 5 to 25, more preferably from 10 to 20, and still more preferably from 14 to 18 microns. Smaller sizes are too small; they may be difficult to retain and abrasive action may be adversely affected, while larger sizes may result in noticeable scratches.

The milled polycrystalline ceramic abrasive particles preferably have an average Vickers hardness of at least 18 GPa, more preferably at least 20 GPa, more preferably at least 22 GPa, more preferably at least 24 GPa, and still more preferably at least 26 GPa.

The milled polycrystalline ceramic abrasive particles preferably have an average fracture toughness of at least 2.2 MPa/m^(1/2), more preferably at least 2.4 MPa/m^(1/2), more preferably at least 2.6 MPa/m^(1/2), more preferably at least 2.8 MPa/m^(1/2), more preferably at least 3.0 MPa/m^(1/2), more preferably at least 3.2 MPa/m^(1/2), more preferably at least 3.4 MPa/m^(1/2), more preferably at least 3.6 MPa/m^(1/2), and even more preferably at least 3.8 MPa/m^(1/2). Lesser fracture toughness values may result in fracture of the abrasive particles and generation of cutting edges which cause scratches that reduce the image clarity of the stone surface.

Suitable alumina-based polycrystalline ceramic abrasive particles and methods for their manufacture are described in, for example, in U.S. Pat. No. 4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,518,397 (Leitheiser et al.); U.S. Pat. No. 4,623,364 (Cottringer et al.); U.S. Pat. No. 4,744,802 (Schwabel); U.S. Pat. No. 4,770,671 (Monroe et al.); U.S. Pat. No. 4,881,951 (Wood et al.); U.S. Pat. No. 4,960,441 (Pellow et al.); U.S. Pat. No. 5,139,978 (Wood); U.S. Pat. No. 5,201,916 (Berg et al.); U.S. Pat. No. 5,366,523 (Rowenhorst et al.); U.S. Pat. No. 5,429,647 (Larmie); U.S. Pat. No. 5,547,479 (Conwell et al.); U.S. Pat. No. 5,498,269 (Larmie); U.S. Pat. No. 5,551,963 (Larmie); U.S. Pat. No. 5,725,162 (Garg et al.); U.S. Pat. No. 6,878,456 (Castro et al.); and in U.S. Pat. Appl. Publ. Nos. 2005/0132656 A1, 2005/0137077 A1, and 2005/0132657 A1.

The abrasive particles are dispersed and retained within the polymeric binder matrix to form shaped composites of the structured abrasive article. Polymeric binder matrix is typically derived from a binder precursor. During the manufacture of the structured abrasive article, the binder precursor is exposed to an energy source which aids in the initiation of the polymerization or curing of the binder precursor. Examples of energy sources include thermal energy and radiation energy, the latter including electron beam, ultraviolet light, and visible light. During this polymerization process, the binder precursor is polymerized and/or cured and thereby converted into a solidified binder. Upon solidification of the binder precursor, the polymeric binder matrix is formed.

Examples of suitable binder precursors include amino resins, alkylated urea-formaldehyde resins, melamine-formaldehyde resins, alkylated benzoguanamine-formaldehyde resins, acrylate resins (including acrylates and methacrylates) such as vinyl acrylates, acrylated epoxies, acrylated urethanes, acrylated polyesters, acrylated acrylics, acrylated polyethers, vinyl ethers, acrylated oils, and acrylated silicones, alkyd resins such as urethane alkyd resins, polyester resins, reactive urethane resins, phenolic resins such as resole and novolac resins, phenolic/latex resins, epoxy resins such as bisphenol epoxy resins, isocyanates, isocyanurates, polysiloxane resins (including alkylalkoxysilane resins), reactive vinyl resins, and phenolic resins (resole and novolac). The resins may be provided as monomers, oligomers, polymers, or combinations thereof. Typically, the resins may have multiple cure sites, which results upon curing in a crosslinked polymeric binder matrix.

The binder precursor can be a condensation curable resin, an addition polymerizable resin, a free-radically-curable resin, and/or combinations and blends of such resins. One binder precursor is a resin or resin mixture that polymerizes via a free-radical mechanism. The polymerization process is initiated by exposing the binder precursor, along with an appropriate catalyst, to an energy source such as thermal energy or radiation energy. Examples of radiation energy include electron beam, ultraviolet light, or visible light.

Examples of free-radically-curable resins include acrylated urethanes, acrylated epoxies, acrylated polyesters, ethylenically-unsaturated monomers, aminoplast monomers having pendant unsaturated carbonyl groups, isocyanurate monomers having at least one pendant acrylate group, isocyanate monomers having at least one pendant acrylate group, and mixtures and combinations thereof. When used generically herein, the term “acrylate” encompasses acrylates and/or methacrylates.

One binder precursor comprises a urethane acrylate oligomer, or a blend of a urethane acrylate oligomer and an ethylenically-unsaturated monomer. Useful ethylenically-unsaturated monomers include, for example, monofunctional acrylate monomers, difunctional acrylate monomers, trifunctional acrylate monomers, acrylate oligomers, and combinations thereof.

Examples of useful acrylated urethanes include those known by the trade designations: “PHOTOMER” (for example, PHOTOMER 6010 aliphatic urethane acrylate oligomer) available from IGM Resins, Waalwijk, The Netherlands; “EBECRYL” (for example, EBECRYL 220 hexafunctional aromatic urethane acrylate of molecular weight 1,000 g/mol, EBECRYL 284 aliphatic urethane diacrylate of 1,200 molecular weight diluted with 1,6-hexanediol diacrylate, EBECRYL 4827 aromatic urethane diacrylate of 1,600 g/mol molecular weight, EBECRYL 4830 aliphatic urethane diacrylate of 1,200 g/mol molecular weight diluted with tetraethylene glycol diacrylate), EBECRYL 6602 (trifunctional aromatic urethane acrylate of 1,300 g/mol molecular weight diluted with trimethylolpropane ethoxy triacrylate), and EBECRYL 840 aliphatic urethane diacrylate of 1,000 g/mol molecular weight), available from Cytec Industries Inc., Smyrna, Ga.; and SARTOMER (for example, SARTOMER 9635, SARTOMER 9645, SARTOMER 9655, SARTOMER 963-B80, and SARTOMER 966-A80), commercially available from Sartomer Company, Exton, Pa.

Ethylenically-unsaturated monomers or oligomers, or acrylate monomers or oligomers, may be monofunctional, difunctional, trifunctional, tetrafunctional, or even of higher functionality. Ethylenically-unsaturated binder precursors include both monomeric and polymeric compounds that contain atoms of carbon, hydrogen, and oxygen, and optionally, nitrogen and the halogens. Ethylenically-unsaturated monomers or oligomers preferably have a molecular weight of less than about 4000 g/mol, and are preferably esters made from the reaction of compounds containing aliphatic monohydroxy groups or aliphatic polyhydroxy groups and unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid. Representative examples of ethylenically-unsaturated monomers include methyl methacrylate, ethyl methacrylate, styrene, divinylbenzene, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, vinyl toluene, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate. Other ethylenically-unsaturated monomers or oligomers include monoallyl, polyallyl, and polymethallyl esters and amides of carboxylic acids, such as diallyl phthalate, diallyl adipate, and N,N-diallyladipamide. Still other nitrogen containing compounds include tris(2-acryloxyethyl)isocyanurate, 1,3,5-tri(2-methacryloxyethyl)-s-triazine, acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, and N-vinylpiperidone. Further examples of ethylenically-unsaturated diluents or monomers can be found in U.S. Pat. No. 5,236,472 (Kirk) and U.S. Pat. No. 5,580,647 (Larson et al.).

In general, the ratio between these acrylate monomers will depend on the weight percent of abrasive particles and any optional additives or fillers desired in the final abrasive article. Typically, these acrylate monomers range from about 5 parts by weight to about 95 parts by weight urethane acrylate oligomer to about 5 parts by weight to about 95 parts by weight ethylenically-unsaturated monomer. Additional information concerning other potential useful binders and binder precursors can be found in U.S. Pat. No. 4,773,920 (Chasman et al.) and U.S. Pat. No. 5,958,794 (Bruxvoort et al.).

Acrylated epoxies are diacrylate esters of epoxy resins such as, for example, the diacrylate esters of bisphenol A epoxy resin. Examples of acrylated epoxies include those available as EBECRYL 3500, EBECRYL 3600, and EBECRYL 3700 from Cytec Industries Inc.; and as CN103, CN104, CN111, CN112, and CN114 from Sartomer Company.

Examples of polyester acrylates include those available as EBECRYL 80, EBECRYL 657, and EBECRYL 830 from Cytec Industries Inc.

Aminoplast monomers have at least one pendant alpha, beta-unsaturated carbonyl group. These unsaturated carbonyl groups may be acrylate, methacrylate or acrylamide type groups. Examples of such materials include N-(hydroxymethyl)acrylamide, N,N′-oxydimethylene-bisacrylamide, ortho- and para-acrylamidomethylated phenol, acrylamidomethylated phenolic novolac, and combinations thereof. These materials are further described in U.S. Pat. No. 4,903,440 (Kirk) and U.S. Pat. No. 5,236,472 (Kirk).

Isocyanurates having at least one pendant acrylate group and isocyanate derivatives having at least one pendant acrylate group are further described in U.S. Pat. No. 4,652,274 (Boettcher). One preferred isocyanurate material is a triacrylate of tris(hydroxyethyl) isocyanurate.

Depending upon how the free-radically-curable resin is cured or polymerized, the binder precursor may further comprise a curing agent (e.g., a thermal initiator or a photoinitiator). When the curing agent is exposed to the appropriate energy source, it will generate a free-radical source that will start the polymerization process.

Another useful binder precursor comprises an epoxy resin. Epoxy resins have an oxirane ring and are polymerized by a ring opening reaction. Such epoxide resins include monomeric epoxy resins and polymeric epoxy resins. Exemplary epoxy resins include diglycidyl ethers of bisphenol A or F such as, for example, those available as EPON 828, EPON 1004, and EPON 1001F from Momentive Specialty Chemicals, Columbus, Ohio, and as DER-331, DER-332, and DER-334, commercially available from Co. Midland, Mich. Other suitable epoxy resins include cycloaliphatic epoxies, glycidyl ethers of phenol formaldehyde novolacs (for example, as available under the trade designations DEN-431 and DEN-428 from Dow Chemical Co.). Examples of usable multi-functional epoxy resins include EPON HPT 1050 and EPON 1031 from Momentive.

Blends of free-radically-curable resins and epoxy resins may be used and are further described in U.S. Pat. No. 4,751,138 (Tumey et al.) and U.S. Pat. No. 5,256,170 (Harmer et al.).

In one embodiment, the polymeric binder, when incorporated with the abrasive particles in the structured abrasive article, has high thermal resistance. Specifically, the cured binder has a glass transition temperature (i.e., T_(g)) of at least 150° C., or at least 160° C., or even at least 175° C. is desired, or at least 200° C.

The polymeric binder matrix and the backing of this disclosure may contain additives such as, for example, abrasive particle surface modification additives (e.g., coupling agents), fillers, expanding agents, fibers, pore formers, antistatic agents, curing agents, suspending agents, wetting agents, photosensitizers, lubricants, surfactants, pigments, dyes, UV stabilizers, and antioxidants. The amounts of these materials are selected to provide the properties desired.

Examples of useful fillers for this disclosure include: metal carbonates (such as calcium carbonate-chalk, calcite, marl, travertine, marble, and limestone; calcium magnesium carbonate, sodium carbonate, and magnesium carbonate), silica (such as quartz, glass beads, glass bubbles, and glass fibers), silicates (such as talc, clays-montmorillonite; feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate, lithium silicate, and hydrous and anhydrous potassium silicate), metal sulfates (such as calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides (such as calcium oxide-lime; aluminum oxide; tin oxide—for example, stannic oxide; titanium dioxide) and metal sulfites (such as calcium sulfite), thermoplastic particles (such as polycarbonate, polyetherimide, polyester, polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal polymers, polyurethanes, nylon particles) and thermosetting particles (such as phenolic bubbles, phenolic beads, polyurethane foam particles). The filler may also be a salt such as a halide salt. Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium chloride, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, and magnesium chloride. Examples of metal fillers include, tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium. Other miscellaneous fillers include sulfur, organic sulfur compounds, graphite, and metallic sulfides. Fillers generally have an average particle size range of 0.1 to 50 microns, typically 1 to 30 microns.

An example of a suspending agent is an amorphous silica particle having a surface area less than 150 meters square/gram, commercially available from DeGussa Corp. Ridgefield Park, N.J., under the trade designation OX-50. The addition of the suspending agent may lower the overall viscosity of the abrasive slurry. The use of suspending agents is further described in U.S. Pat. No. 5,368,619 (Culler).

A coupling agent may provide an association bridge between the binder and the abrasive particles, and any filler particles. Examples of coupling agents include silanes, titanates, and zircoaluminates. The coupling agent can be added directly to the binder precursor, which may have about 0 to 30 percent by weight, preferably 0.1 to 25 percent by weight coupling agent. Alternatively, the coupling agent can be applied to the surface of any particles, typically about 0 to 3% by weight coupling agent, based upon the weight of the particle and the coupling agent. Examples of commercially available coupling agents include SILQUEST A-174 (gamma-methacryloxypropyltrimethoxysilane) coupling agent, commercially available from GE Advanced Materials, Wilton, Conn. Still another example of a commercial coupling agent is an isopropyl triisostearoyl titanate, available as KR-TTS from Kenrich Petrochemicals, Bayonne, N.J.

The binder precursor may further comprise a curing agent. A curing agent is a material that helps to initiate and complete the polymerization or crosslinking process such that the binder precursor is converted into a binder. The term “curing agent” encompasses initiators (e.g. thermal initiators and photoinitiators), catalysts, and activators. The amount and type of the curing agent will depend largely on the chemistry of the binder precursor.

Polymerization of ethylenically-unsaturated monomer(s) or oligomer(s) occurs via a free-radical mechanism. If the energy source is an electron beam, or ionizing radiation source (gamma or x-ray), free-radicals which initiate polymerization are generated. However, it is within the scope of this disclosure to use initiators even if the binder precursor is exposed to an electron beam. If the energy source is heat, ultraviolet light, or visible light, an initiator may have to be present in order to generate free-radicals. Examples of initiators that generate free-radicals upon exposure to ultraviolet light or heat include, but are not limited to, organic peroxides, azo compounds, quinones, nitroso compounds, acyl halides, hydrazones, mercapto compounds, pyrylium compounds, imidazoles, chlorotriazines, benzoin, benzoin alkyl ethers, diketones, phenones, and mixtures thereof. Examples of commercially available photoinitiators that generate free-radicals upon exposure to ultraviolet light include those available as IRGACURE 651, IRGACURE 184, IRGACURE 369, and DAROCUR 1173 from Ciba Specialty Chemicals, Tarrytown, N.Y. Examples of initiators that generate free-radicals upon exposure to visible light may be found in U.S. Pat. No. 4,735,632 (Larson et al.).

Typically, the initiator is used in amounts ranging from 0.1 to 10 percent by weight, preferably 2 to 4 percent by weight, based on the total weight of the binder precursor. Additionally, it is preferred to disperse, preferably uniformly disperse, the initiator in the binder precursor prior to the addition of any particulate material, such as the abrasive particles and/or filler particles.

In general, it is preferred that the binder precursor be exposed to radiation energy, preferably ultraviolet light or visible light. In some instances, certain abrasive particles and/or certain additives will absorb ultraviolet and visible light, which makes it difficult to properly cure the binder precursor. This phenomenon is especially true with ceria abrasive particles and silicon carbide abrasive particles. It has been found, quite unexpectedly, that the use of phosphate-containing photoinitiators, in particular acylphosphine oxide containing photoinitiators, tends to overcome this problem. An example of such a photoinitiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, commercially available from BASF Corporation, Charlotte, N.C., as LUCIRIN TPO. Other examples of commercially available acylphosphine oxides include those available as DAROCUR 4263 and DAROCUR 4265 from Ciba Specialty Chemicals.

Optionally, the curable compositions may contain photosensitizers or photoinitiator systems which affect polymerization either in air or in an inert atmosphere, such as nitrogen. These photosensitizers or photoinitiator systems include compounds having carbonyl groups or tertiary amino groups and mixtures thereof. Among the preferred compounds having carbonyl groups are benzophenone, acetophenone, benzil, benzaldehyde, o-chlorobenzaldehyde, xanthone, thioxanthone, 9,10-anthraquinone, and other aromatic ketones which may act as photosensitizers. Among the preferred tertiary amines are methyldiethanolamine, ethyldiethanolamine, triethanolamine, phenylmethylethanolamine, and dimethylaminoethyl benzoate. In general, the amount of photosensitizer or photoinitiator system may vary from about 0.01 to 10% by weight, more preferably from 0.25 to 4.0 percent by weight, based on the weight of the binder precursor. Examples of photosensitizers include those available as QUANTICURE ITX, QUANTICURE QTX, QUANTICURE PTX, and QUANTICURE EPD from Biddle Sawyer Corp., New York, N.Y.

In one embodiment, the binder precursor is cured with the aid of both a photoinitiator (e.g., as described hereinabove) and a thermal initiator acting on the same functional type. Examples of thermal initiators include organic peroxides (e.g., benzoyl peroxide), azo compounds, quinones, nitroso compounds, acyl halides, hydrazones, mercapto compounds, pyrylium compounds, imidazoles, chlorotriazines, benzoin, benzoin alkyl ethers, diketones, phenones, and mixtures thereof. Examples of suitable azo compound thermal initiators include those available as VAZO 52, VAZO 64, and VAZO 67 from E.I. du Pont de Nemours and Co., Wilmington, Del.

Structured abrasive articles according to the present disclosure can be made using known methods for making structured abrasive articles having shaped abrasive composites. Useful methods are described in U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,672,097 (Hoopman); U.S. Pat. No. 5,681,217 (Hoopman et al.); and U.S. Pat. No. 5,435,816 (Spurgeon et al.); U.S. Pat. No. 5,454,844 (Hibbard et al.), U.S. Pat. No. 5,851,247 (Stoetzel et al.); U.S. Pat. No. 6,139,594 (Kincaid et al.); and U.S. Pat. No. 5,304,223 (Pieper et al.); and in U.S. Pat. No. 5,437,754 (Calhoun). Another useful method of making useful abrasive articles having shaped abrasive composites where the composites comprise abrasive agglomerates fixed in a make coat, with optional size coatings, is described in U.S. Pat. No. 6,217,413 (Christianson).

The structured abrasive article may be shape converted using a process such, for example, as rule die cutting, laser cutting, or water jet cutting.

SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE

In a first embodiment, the present disclosure provides a method of finishing a stone surface, the method comprising:

providing a structured abrasive article comprising a structured abrasive layer adhered to a major surface of a backing, the structured abrasive layer comprising shaped abrasive composites adhered to the major surface, the shaped abrasive composites comprising milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a median particle size D₅₀ of from 3 to 30 microns;

frictionally contacting the structured abrasive layer with the stone surface; and

moving the structured abrasive layer relative to the stone surface under conditions sufficient to finish the stone surface.

In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the structured abrasive layer has a bearing area ratio of from 40 percent to 70 percent.

In a third embodiment, the present disclosure provides a method according to the first or second embodiment, wherein the milled polycrystalline ceramic abrasive particles comprise milled polycrystalline alumina particles.

In a fourth embodiment, the present disclosure provides a method according to any one of the first to third embodiments, wherein the shaped abrasive composites comprise hexagonal posts.

In a fifth embodiment, the present disclosure provides a method according to any one of the first to fourth embodiments, wherein the milled polycrystalline ceramic abrasive particles have an average Vickers hardness of at least 21 gigapascals.

In a sixth embodiment, the present disclosure provides a method according to any one of the first to fifth embodiments, wherein the milled polycrystalline ceramic abrasive particles have an average fracture toughness of at least 3 megapascals per meter^(0.5).

In a seventh embodiment, the present disclosure provides a method according to any one of the first to sixth embodiments, wherein the stone surface comprises at least a portion of a floor.

In an eighth embodiment, the present disclosure provides a method according to any one of the first to seventh embodiments, wherein the stone surface comprises at least a portion of a counter.

In a ninth embodiment, the present disclosure provides a method according to any one of the first to eighth embodiments, wherein the stone surface comprises at least one of a granite surface, a marble surface, a cement surface, a terrazzo surface, a ceramic tile surface, or a concrete surface.

In a tenth embodiment, the present disclosure provides a method according to any one of the first to ninth embodiments, wherein the backing is secured to a lofty open nonwoven backup pad mounted on a rotary floor machine, wherein the rotary floor machine operates at a rotational speed of less than 250 rotations per minute.

In an eleventh embodiment, the present disclosure provides a structured abrasive article comprising a structured abrasive layer adhered to a major surface of a backing, wherein the structured abrasive layer comprises shaped abrasive composites adhered to the major surface, wherein the shaped abrasive composites comprise milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a mean particle size D₅₀ of from 3 to 30 microns.

In a twelfth embodiment, the present disclosure provides a structured abrasive article according to the eleventh embodiment, wherein the structured abrasive layer has a bearing area ratio of from 40 percent to 70 percent.

In a thirteenth embodiment, the present disclosure provides a structured abrasive article according to the eleventh or twelfth embodiment, wherein the milled polycrystalline ceramic abrasive particles comprise milled polycrystalline alumina particles.

In a fourteenth embodiment, the present disclosure provides a structured abrasive article according to any one of the eleventh to thirteenth embodiments, wherein the abrasive composites comprise hexagonal prisms.

In a fifteenth embodiment, the present disclosure provides a structured abrasive article according to any one of the eleventh to fourteenth embodiments, wherein the milled polycrystalline ceramic abrasive particles have an average Vickers hardness of at least 21 gigapascals.

In a sixteenth embodiment, the present disclosure provides a structured abrasive article according to any one of the eleventh to fifteenth embodiments, wherein the milled polycrystalline ceramic abrasive particles have an average fracture toughness of at least 3 megapascals per meter^(0.5).

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. The abbreviations listed in Table 1 (below) are used throughout the examples.

TABLE 1 ABBREVIATION DESCRIPTION TMPTA trimethylolpropane triacrylate; commercially available as SR 351 from Sartomer Co., Exton, Pennsylvania PH2 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone photoinitiator, available as IRGACURE 369 from Ciba Specialty Chemicals, Tarrytown, New York THI 2,2′-azobis(2,4-dimethylpentanenitrile) thermal initiator, available as VAZO 52 from E.I. du Pont de Nemours and Co., Wilmington, Delaware CAS surface-modified calcium metasilicate filler, available as WOLLASTOCOAT M400 from NYCO, Willsboro, New York SCA silane coupling agent, 3-methacryloxypropyltrimethoxysilane, available as SILQUEST A-174NT from Momentive Specialty Chemicals, Columbus, Ohio ASF amorphous silica filler, available as AEROSIL OX-50 FUMED SILICA from Evonik Industries AG, Essen, Germany BYK wetting agent, available as BYK 985 from BYK USA Inc., Wallingford, Connecticut PR phenolic resin, water-based, available as Liquid Phenolic Resin 80 5077A from Arclin, Mississauga, Ontario, Canada TAL talc filler, available as MISTRON 353 from Imerys Talc America, Inc., Three Forks, Montana DYN surfactant, available as DYNOL 604 from Air Products and Chemicals, Allentown, Pennsylvania H2O tap water 3u CAO milled ceramic aluminum oxide, 3 microns average particle size, prepared according to the disclosure of U.S. Pat. No. 5,312,789 (Wood), and obtained from Fujimi Corp., Tulatin, Oregon 4u CAO milled ceramic aluminum oxide, 4 microns average particle size, prepared according to the disclosure of U.S. Pat. No. 5,312,789 (Wood), and obtained from Fujimi Corp. 6u CAO milled ceramic aluminum oxide, 6 microns average particle size, prepared according to the disclosure of U.S. Pat. No. 5,312,789 (Wood), and obtained from Fujimi Corp. 800 CAO milled ceramic aluminum oxide, available as CUBITRON 321 grade JIS 800, approx. 16 microns average particle size 180 CAO milled ceramic aluminum oxide, available as CUBITRON 321 grade grade ANSI 180, approx. 78 microns average particle size 2500 WAO white fused aluminum oxide, grade JIS 2500, available from Treibacher Schleifmittel, Villach, Austria PDP lofty, non-woven diamond (approx. 4 microns average particle size) abrasive pad, available as 3M SCOTCHBRITE PURPLE DIAMOND FLOOR PAD PLUS, from 3M Company, St. Paul, Minnesota A10 diamond structured abrasive disc (approx. 10 microns average particle size) available as 3M TRIZACT INDUSTRIAL DIAMOND QRS CLOTH 673FA, A10 YF-WEIGHT from 3M Company A45 diamond structured abrasive disc (approx. 45 microns average particle size) available as 3M TRIZACT INDUSTRIAL DIAMOND QRS CLOTH 673FA, A45 YF-WEIGHT from 3M Company A300 diamond structured abrasive disc (approx. 170 micron average particle size) available as 3M TRIZACT INDUSTRIAL DIAMOND QRS CLOTH 673FA, A300 YF-WEIGHT from 3M Company CT unglazed ceramic quarry tile, available as VERSATILE from Metropolitan Ceramics, Canton, Ohio PCT precast cementitious terrazzo tile, 12-inch (30 cm) square, item WT2774, available from Wausau Tile, Wausau, Wisconsin GMG Grey Maua Granite tile, 8-inch 20 cm) square, available from Braminas Brasilerira de Granitos e Marmores Ltd, Sao Paulo, Brazil

Procedure for Making Structured Abrasive Articles (Method 1)

Structured abrasive articles were prepared according to the procedure of Example 2 as described in col. 19, line 1 to col. 20, line 4 of U.S. Pat. No. 8,323,072 (Billig et al.). The abrasive slurries used to create the shaped abrasive composites were formulated according to the compositions reported in Table 2 (below).

TABLE 2 COMPOSITION, grams 800 180 2500 EXAMPLE TMPTA PH2 THI CAS SCA ASF BYK CAO CAO WAO 1 9552 96 96 8661 372 87 0 11136 0 0 2 9552 96 96 8661 372 87 0 11136 0 0 3 9552 96 96 8661 372 87 0 11136 0 0 4 9552 96 96 8661 372 87 0 11136 0 0 5 9552 96 96 8661 372 87 0 11136 0 0 6 9552 96 96 8661 372 87 0 11136 0 0 7 9552 96 96 8661 372 87 0 11136 0 0 Comparative 6210 62.5 0 6090 305 142.5 0 0 12190 0 Example A Comparative 8230 82.5 0 4962.5 0 150 37.5 0 0 11537.5 Example B

Structured abrasive discs were assembled by laminating the backings of the structured abrasive articles prepared above to KANEBO 2K3 nylon loop fastening material from Kanebo Bell Ltd. New York, N.Y. using 3M ADHESIVE TRANSFER TAPE 9485PC from 3M Company, and compressing the assembly through a pneumatic roll laminator set at 100 psi (0.7 MPa) roll pressure. Five inch (13 cm) diameter abrasive discs were die-cut from the laminated assembly using a circular rule die.

Procedure for Making Non-Structured Lofty Non-Woven Abrasive Articles (Method 2)

Water-based phenolic abrasive slurries for making lofty, non-woven abrasive articles were formulated according to the compositions reported in Table 3 (below).

TABLE 3 COMPOSITION, grams 3u 4u 6u EXAMPLE PR TAL CAS DYN H2O CAO CAO CAO Comparative 227.5 31.9 4.5 10 100.0 0 0 91.0 Example C drops Comparative 227.5 32.1 4.3 10 100.1 91.0 0 0 Example D drops Comparative 227.4 32.1 4.3 10 100.1 0 91.2 0 Example E drops

Eight-inch (20-cm) discs were die-cut from ⅝ inch (1.6 cm) thick 200 denier nylon non-woven material. The lofty nonwoven nylon prebond had a basis weight of 500 g/m². The nylon prebond discs were saturated with abrasive slurry and the excess slurry squeezed out between rubber nip rollers under 80 psi (0.6 MPa) roll pressure. Wet slurry add-on weight was 165-169 percent by weight. The wet prebond discs were cured for 30 minutes in a circulating-air oven set at 300° F. (149° C.).

Surface Roughness Measurement

The surface roughness is defined by R_(a) and R_(z). The R_(a) of a surface is the measurement of the arithmetic average of the scratch depth. It is the average of 5 individual roughness depths of five successive measuring lengths, where an individual roughness depth is the vertical distance between the highest point and a center line. R_(z) is the average of 5 individual roughness depths of a measuring length, where an individual roughness depth is the vertical distance between the highest point and the lowest point. R_(a) and R_(z) were measured at the end of each 3-minute process step using a Mahr Perthometer M2 contact profilometer from Mahr Corporation, Cincinnati, Ohio. Reported values were the average of six measurements on each test tile specimen.

Test Method 1

A 4-foot (1.2-m)×5-foot (1.5-m) area of 12-inch (30-cm) square red marble flooring tiles was wet-abraded and finished according to the following steps.

Interface attachment discs having hooks on both surfaces were used to attach abrasive test discs to a floor machine driver pad. Interface attachment discs were formed by laminating sheets of adhesive-backed reclosable fastener similar to those available under the trade designation 3M DUAL LOCK LOW PROFILE RECLOSABLE FASTENER SJ4570 from 3M Company, and then die-cutting 5 inch (13-cm) diameter interface attachment discs.

Four 5-inch (13-cm) structured abrasive test discs were attached at the 12:00, 3:00, 6:00 and 9:00 positions on the outer perimeter of a lofty. 17-inch (43-cm) nonwoven machine driver pad obtained as 3M WHITE SUPERPOLISH PAD 4100 from 3M Company. The abrasive discs and driver pad were attached to a 17-inch (43-cm) SEARAY 175 swing-type floor machine from Pacific Floorcare, Muskegon, Mich. The machine was operated at 175 rpm. The test floor surface was wetted with water, and each set of abrasive discs was tested by making six successive passes over the red marble test area.

Test Method 2

Square test tile specimens were placed on a layer of ⅛ inch (32 mm) thick high-density foam attached to a benchtop surface to hold tile specimens in place for abrasive preparation and finishing. A continuous water stream was directed onto the test tile surface at an approximately 30 ml/minute flow rate for wet-abrasive preparation steps. Finishing steps were conducted with no water flow, and only after a previously-prepared wetted surface had dried completely.

Structured abrasive articles were mounted to a 5-inch (13 cm) hook-type back-up pad (item 915 from 3M Company) and rotated at 1000 rpm using a variable-speed rotary polishing tool (model 28391) from 3M Company. Non-structured, lofty non-woven abrasive articles were mounted to a 6-inch (15 cm) hook-type back-up pad (item 916 from 3M Company) and rotated at 1400 rpm using the rotary polishing tool.

All preparation and finishing process steps were carried out for three successive one-minute intervals, rotating the tile 90° counterclockwise between each finishing step. The polishing tool was operated under light downward hand pressure and was circulated across the entire test tile holding the abrasive article flat to the tile surface to produce a uniformly-finished surface.

Aesthetic measurements for Examples 9-12 and Comparative Examples H-K were made using a RHOPOINT IQ 20 60. DOI gloss haze meter. Aesthetic measurements for Examples 13-17 and Comparative Examples L-Q were made using a RHOPOINT NOVO-GLOSS IQ goniophotometer. Both Rhopoint instruments were obtained from Imbotec Industrial Solutions. Ontario, Canada. Reported values were the average of six measurements on each test tile specimen.

Example 8 and Comparative Examples F and G

Structured abrasive discs incorporating milled polycrystalline ceramic abrasive particles and micron-grade white fused alumina were tested on an array of 12 inches×12 inches (30 cm by 30 cm) red marble tiles. Four 5-inch (13-cm) diameter structured abrasive discs made according to Method 1 were used on the 17-inch (43-cm) SEARAY 175 swing-type floor machine. Mechanical surface scratch profiles were measured before and after each abrading step to gauge the surface refinement capability of non-diamond abrasives on marble.

Surface roughness data reported in TABLE 4 (below) are the average of six measurements taken on at least six tile locations, using a Mahr Perthometer M2 profilometer from Mahr Corporation, Cincinnati, Ohio.

TABLE 4 R_(a), R_(z), microinches microinches EXAMPLE STEP PROCEDURE/COMMENTS (microns) (microns) 0 Starting condition finished 4.8 (0.12) 49 (1.2) using a PDP pad dry. Specular glossy appearance. Comparative 1 Abraded using A100 discs wet. 18.3 (0.465) 165 (4.19) Example F No low-angle reflected image. Matte appearance 8 2 Finished using Example 1 discs 8.4 (0.21) 82 (2.1) wet. Distinct low-angle reflected image. Glossy appearance. Comparative 3 Finished using A6 discs wet. 10.2 (0.259) 85 (2.2) Example G Indistinct low-angle reflective image. Semi-glossy appearance

In Table 4, each step 1 to 4 was carried out consecutively.

Profilometric measurements in Table 4 show the ability of structured abrasive articles according to the present disclosure to finish the surface of marble floor material. Unexpectedly, use of significantly finer-grade conventional fused alumina (Step 4) did not further refine the surface, and produced a visually degraded aesthetic appearance.

Examples 9-12 and Comparative Examples H-K

Lofty, non-woven abrasives were produced with milled polycrystalline ceramic aluminum oxide abrasive mineral of varying sizes, as described in Method 2 and Table 3. Cured pad specimens were tested on 6-inch (15-cm) unglazed ceramic quarry tiles (CT) according to Test Method 2, which were previously wet-polished using A45 and A10 abrasives. Results are reported in Table 5 (below).

TABLE 5 R_(a), PROCEDURE/ microinch 20° 60° 20° EXAMPLE TILE COMMENTS (micron) GLOSS GLOSS DOI Comparative 1 Initial 38.3 (0.97) 1.5 6.2 21.4 Example H Finished using 26.1 (0.66) 15.8 43.6 21.7 a PDP pad dry 9 1 Initial 32.6 (0.83) 1.5 6.2 21.4 Finished using 20.5 (0.52) 9.6 40.9 6.5 6u CAO pad dry Comparative 2 Initial 32.2 (0.82) 1.1 4.1 2.6 Example I Finished using 24.6 (0.62) 10.9 34.5 18.6 a PDP pad dry 10 2 Initial 27.9 (0.71) 1.1 3.7 5.4 Finished using 27.4 (0.70) 1.6 9.9 5.3 3u CAO pad dry Comparative 3 Initial 24.4 (0.62) 1.2 4.8 8.3 Example J Finished using 19.4 (0.49) 10.3 32.2 25.5 a PDP pad dry 11 3 Initial 26.7 (0.68) 1.1 4.6 5.4 Finished using 23.5 (0.60) 4.0 18.2 11.4 4u CAO pad dry Comparative 4 Initial 28.7 (0.73) 1.1 3.9 5.4 Example K Finished using 25.2 (0.64) 13.3 39.3 22.4 a PDP pad dry 12 4 Initial 27.2 (0.69) 1.1 3.7 3.7 Finished using 24.8 (0.63) 15.4 37.6 64.5 Example 2 disc dry

The results in Table 5 show that when utilized in lofty, nonwoven constructions, milled polycrystalline ceramic aluminum oxide with particle sizes comparable to the diamond abrasive particles contained in PDP achieve inferior aesthetic quality. When utilized in a rigid, structured abrasive construction, milled polycrystalline ceramic aluminum oxide of 16-micron particle size (4 times larger than the diamond abrasive particles in PDP), achieved superior surface quality. This is indicated by a three-fold greater image clarity compared to PDP, with image brightness comparable to PDP.

Examples 13-14 and Comparative Example L

Structured abrasive articles were produced as described in Method 1 and Table 2 above. Structured abrasive articles were compared against PDP lofty nonwoven abrasives to show the dry finishing efficacy of a rigid structured abrasive article construction on unglazed ceramic tile (CT). In these Examples, unglazed ceramic tiles (CT) were initially prepared with a 120-grit resin-bond grinding wheel, followed by pre-finishing with A45 and A10 in succession, according to Method 2. In these Examples, the important “Haze” aesthetic measurement was included for the comparison. Results are summarized in Table 6 (below).

TABLE 6 R_(a), R_(z), PROCEDURE/ microinch microinch 60° 60° EXAMPLE COMMENTS (micron) (micron) GLOSS HAZE DOI Comparative Initial 23 (0.58) 231 (5.87) 18.2 3.8 86.0 Example L Finished using 19 (0.48) 220 (5.59) 53.5 10.5 81.1 PDP pad dry 13 Initial 22 (0.56) 248 (6.30) 17.2 3.5 86.5 Finished using 19 0.48) 220 (5.59) 40.9 6.3 93.1 the Example 3 disc dry 14 Initial 22 (0.56) 226 (5.74) 6.6 1.2 78.7 Finished using 19 (0.48) 209 (5.31) 13.0 4.0 76.1 A10 disc dry Finished using 19 (0.48) 236 (5.99) 44.8 8.7 92.4 the Example 4 disc dry

As shown in Table 6, the R_(a) and R_(z) surface profilometric measurements indicated little macroscopic surface roughness refinement whether using diamond abrasive particles or milled ceramic aluminum oxide abrasive particles in lofty nonwoven or rigid abrasive constructions, beneath the initial starting surface

The aesthetic data in Table 6 show that use of 4-micron diamond abrasive particles in PDP construction reduced reflected image clarity compared to the initial starting surface, but increased the 60° gloss (the image brightness level). Haze increased ˜2.8× after finishing with 4-micron diamonds abrasives in PDP. The 16-micron milled ceramic aluminum oxide abrasive particles abrasive used in Example 13 and Example 14 produced significantly increased t DOI image clarity, with a slightly lesser gloss attainment, and an ˜1.8× increase in haze.

Example 15 and Comparative Example M

Precast cementitious terrazzo tiles (PCT) were cut into 6-inch (15-cm) square specimens using a water-cooled diamond tile-cutting saw. The terrazzo specimens were used to illustrate finishing performance on a soft inorganic composite surface. The Portland cement-based Wausau tiles have a high sand content and a relatively weak bond phase. While easily abraded, the soft surface made it difficult to produce a very high aesthetic quality as reported in Table 7. In these Examples, the tests were conducted according to Test Method 2, and the precast cementitious terrazzo tiles were initially prepared using A45 and A10 in succession, prior to final finishing. Factory-produced surface characteristics for the terrazzo tiles are included in Table 7 (below) for reference.

TABLE 7 R_(a), R_(z), PROCEDURE/ microinches microinches 60° 60° EXAMPLE COMMENTS (microns) (microns) GLOSS HAZE DOI Factory-finished 69 (1.75)  544 (13.82) 37.0 3.1 87.0 surface Comparative Initial 31 (0.79) 284 (7.21) 4.9 1.0 27.3 Example M Finished using 40 (1.02) 386 (9.80) 40.0 14.9 46.9 PDP pad dry Example 15 Initial 31 (0.79) 284 (7.21) 4.9 1.0 27.3 Finished using 25 (0.64) 272 (6.91) 15.9 4.9 68.6 the Example 5 disc dry

In the examples reported in Table 7 (above), neither the 4-micron PDP pad of Comparative Example M nor the 16-micron Example 5 structured abrasive disc in Example 15 produced a surface quality comparable to the factory-finished surface. However, the Example 5 structured abrasive disc increased DOI 2.5× over the intermediate pre-finished surface produced by A10 structured abrasive disc, whereas the PDP used for Comparative Example M increased DOI 1.7× over the initial pre-finished surface. Significantly, the lofty non-woven PDP used for Comparative Example M increased haze 15× over the initial pre-finished surface, whereas in Example 15 the Example 5 structured abrasive disc increased haze only 5× over the initial pre-finished surface.

Example 16 and Comparative Examples N-O

Samples of Grey Maua granite (GMG) were used to test finishing performance on very hard natural stone surfaces. The 8-inch (20-cm) square granite tiles were cut into 4-inch (10-cm) square specimens using a water-cooled diamond tile-cutting saw. In accordance with Test Method 2, the rough, wire-sawn back surface of the granite tiles produced from the stone quarry was ground and prepared using A300, A45, and A10 discs in succession and final finishing steps were conducted. Test results are reported in Table 8. Factory-produced surface characteristics for the granite tiles are included in Table 8 (below) for reference.

TABLE 8 R_(a), R_(z), PROCEDURE/ microinches microinches 60° 60° EXAMPLE COMMENTS (microns) (microns) GLOSS HAZE DOI Factory-polished 16 (0.41)  176 (4.47) 64.2 5.3 91.6 surface Comparative Initial 10 (0.25)  102 (2.59) 7.2 1.2 74.9 Example N Finished using 9 (0.23)  99 (2.51) 71.4 9.3 75.7 PDP pad dry Comparative Initial 9 (0.23) 137 (3.48) 7.9 1.4 81.4 Example O Finished using 7 (0.18)  85 (2.16) 47.6 11.3 76.9 6u CAO pad dry Example 16 Initial 11 (0.28)  124 (3.15) 9.3 1.7 86.3 Finished using 9 (0.23) 104 (2.64) 54.9 4.9 95.7 the Example 6 disc dry

Neither Comparative Example N nor Comparative Example O achieved aesthetic surface quality comparable to the factory-produced finish. While reflected image brightness was acceptable in both of Comparative Examples N and O, which were lofty open nonwoven constructions. Reflected image clarity as measured by DOI was significantly less than the factory-produced surface for both lofty non-woven Comparative Examples N and O. Both Comparative Examples N and O yielded haze levels twice those of the factory-produced surface. Example 16 achieved comparable brightness to the factory-produced surface, and further, produced haze and DOI levels better than the factory-polished surface.

Example 17 and Comparative Examples P-Q

Six-inch (15 cm) square tile specimens were cut from a 1.5-inch (3.8 cm) thick, cured, unreinforced concrete slab using a water-cooled diamond tile-cutting saw. The steel-troweled surface of the concrete specimens was tested. In these Examples, the steel-troweled test surfaces were first prepared for final finishing using A300, A45, and A10 discs in succession, all according to Test Method 2. The results are summarized in Table 9 (below).

TABLE 9 R_(a), R_(z), PROCEDURE/ microinches microinches 60° 60° EXAMPLE COMMENTS (microns) (microns) GLOSS HAZE DOI Comparative Initial 26 (0.66) 280 (7.11) 6.4 1.4 63.5 Example P Finished using 18 (0.46) 197 (5.00) 66.3 15.9 59.5 PDP pad dry Comparative Initial 28 (0.71) 273 (6.93) 8.4 2.2 56.0 Example Q Finished using 16 (0.41) 212 (5.38) 15.8 5.4 56.9 A10 disc dry Example 17 Initial 28 (0.71) 286 (7.26) 8.4 1.8 70.0 Finished using 16 (0.41) 190 (4.83) 30.4 5.4 84.5 the Example 7 disc dry

As shown in Table 9 (above). Comparative Example P (PDP pad), using a 4-micron diamond pad, yielded significantly increased gloss, but decreased DOI, and resulted in a large increase in haze over the initial surface condition. Comparative Example Q (A10 disc dry), using 10-micron diamond abrasives, yielded a modestly increased gloss, and unchanged DOI. Example 17 (Example 7 disc dry), using 16-micron milled polycrystalline ceramic aluminum oxide abrasive, yielded a moderate gloss increase and significantly increased DOI.

All cited references, patents, or patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto. 

1. A method of finishing a stone surface, the method comprising: providing a structured abrasive article comprising a structured abrasive layer adhered to a major surface of a backing, the structured abrasive layer comprising shaped abrasive composites adhered to the major surface, the shaped abrasive composites comprising milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a median particle size D₅₀ of from 3 to 30 microns and wherein the backing is secured to a lofty open nonwoven backup pad mounted on a rotary floor machine, wherein the rotary floor machine operates at a rotational speed of less than 250 rotations per minute; frictionally contacting the structured abrasive layer with the stone surface; and moving the structured abrasive layer relative to the stone surface under conditions sufficient to finish the stone surface.
 2. A method according to claim 1, wherein the structured abrasive layer has a bearing area ratio of from 40 percent to 70 percent.
 3. (canceled)
 4. A method according to claim 1, wherein the shaped abrasive composites comprise hexagonal posts.
 5. A method according to claim 1, wherein the milled polycrystalline ceramic abrasive particles have an average Vickers hardness of at least 21 gigapascals.
 6. A method according to claim 1, wherein the milled polycrystalline ceramic abrasive particles have an average fracture toughness of at least 3 megapascals per meter^(0.5).
 7. A method according to claim 1, wherein the stone surface comprises at least a portion of a floor.
 8. A method according to claim 1, wherein the stone surface comprises at least a portion of a counter.
 9. A method according to claim 1, wherein the stone surface comprises at least one of a granite surface, a marble surface, a cement surface, a terrazzo surface, a ceramic tile surface, or a concrete surface.
 10. (canceled)
 11. A structured abrasive article comprising a structured abrasive layer adhered to a major surface of a backing, wherein the structured abrasive layer comprises shaped abrasive composites adhered to the major surface, wherein the shaped abrasive composites comprise milled polycrystalline ceramic abrasive particles retained in a polymeric binder, wherein the milled polycrystalline ceramic abrasive particles have a mean particle size D₅₀ of from 14 to 18 microns, and wherein the milled polycrystalline ceramic abrasive particles comprise milled polycrystalline alumina particles.
 12. The structured abrasive article of claim 11, wherein the structured abrasive layer has a bearing area ratio of from 40 percent to 70 percent.
 13. (canceled)
 14. The structured abrasive article of claim 11, wherein the abrasive composites comprise hexagonal prisms.
 15. The structured abrasive article of claim 11, wherein the milled polycrystalline ceramic abrasive particles have an average Vickers hardness of at least 21 gigapascals.
 16. The structured abrasive article of claim 11, wherein the milled polycrystalline ceramic abrasive particles have an average fracture toughness of at least 3 megapascal-meter^(−0.5). 